The present invention generally relates to an optical radiation sensor device, and more particularly to a sensor device incorporating a photosensor.
Lignt sensors are used in a large number of different applications. In such light sensing applications, several characteristics of the sensing mechanism need to be in acceptable ranges and some further need to be characterized for specific light sensing applications. Other characteristics of the sensor may increase the range of applications for which the sensor is suitable and/or may provide for easier or more economical design applications. One characteristic for which general requirements vary significantly from one application to another is the angular response characteristic, i.e., the angular response profile, of the sensor which is needed for the particular application. A second characteristic is the optical gain, which for low light level measurements is preferably high enough to make stable measurements of the lowest light levels which need to be detected by the system.
Sensor devices of the type used to detect light are constructed in a variety of packages. For example, photoresistive sensors are often mounted on a circuit board with or without a separate lens positioned in front of the sensor. Some photodiodes have been constructed in which the sensor die is mounted to a lead frame and is encapsulated by a clear epoxy. A portion of the epoxy encapsulant is molded into a lens so as to focus incident light onto the sensor die. Such lenses have been either spherical or other surfaces of revolution that are symmetric about an axis which is generally perpendicular to the surface of the active sensing element. Additionally, these lenses exhibit a single focal length. Unlike a sensor construction in which a separate lens is spaced from the sensor, the lens in these types of sensor devices is an integral part of the sensor and the space separating the sensor and the lens has been eliminated. The main design difference which results from filling the space between the lens and the sensor with plastic is that the speed of propagation of the light rays is reduced being inversely proportional to the index of refraction of the lens material. This effectively increases the focal length of the lens in proportion to the index of refraction of the material.
For certain applications, it is desired to have a field of view which is different in one direction than in the transverse direction. One such application is a headlamp control system in which vehicle headlamps are turned on and off in response to a sensed ambient light level. U.S. Pat. No. 6,243,002 issued to Hill et al. discloses a headlamp control system in which the vertical field of view of a sensor is different from the horizontal field of view. These different fields of view are obtained by providing a field-defining channel in the housing in which the sensor is mounted. Such a configuration, however, requires the channel, and hence the housing, to have significant depth, and that the sensor be mounted within the housing spaced away from the outer surface of the housing by an amount equal to at least the depth of the channel. If the aforementioned sensor device having a lead frame is utilized, the circuit board on which the sensor device is mounted would need to be spaced all the farther away from the surface of the housing to accommodate a significant portion of the length of the sensor device and the depth of the channel.
It is also desirable to make the sensor device as small as possible for certain applications, such as when the sensor is incorporated in a rearview mirror assembly for use in controlling vehicle headlamps, windshield wipers, or controlling an electrochromic mirror element provided in the rearview mirror assembly. Present photosensors generally have active sensing areas in the range of 1 mm2 to 100 mm2. To provide such large photosensors in a mirror assembly or other device, relatively large apertures need to be provided in the housing of the structure in which the sensor is provided. Despite the desirability for decreasing the size of the photosensor, one cannot arbitrarily decrease the size of the active sensing area of the photosensor because the photosensor then becomes subject to problems associated with lens defects that can cause shadowing to occur. Further, using such a small detector reduces the optical gain and the angular response of the sensor. When a very small sensing element is utilized in combination with a lens where the sensing element placed at the lens focus, the sensing element can only sense light that impinges on the lens on-axis, and is almost blind to all off-axis light.
Accordingly, there exists a need for a smaller photosensor device that exhibits optical gain and an angular response approaching or exceeding that of larger photosensors. Also, there exists the need for a sensor device construction that provides different fields of view in transverse directions without requiring a channel to restrict the field of view.
Accordingly, it is an aspect of the present invention to provide a sensor device providing different fields of view in transverse directions. To achieve this and other aspects and advantages, a sensor device of the present invention comprises a support structure; a sensing element mounted on the support substrate for sensing optical radiation and generating an electrical output signal in response thereto; and an encapsulant encapsulating the sensing element on the support structure, the encapsulant including an integral anamorphic lens.
According to another aspect of the present invention, a sensor device comprises a support structure; a sensing element mounted on the support structure for sensing optical radiation and generating an electrical signal in response thereto; and an encapsulant encapsulating the sensing element on the support structure, the encapsulant including an integral lens for directing incident optical radiation towards the sensing element, the lens presenting different fields of view to the sensing element for transverse directions.
According to yet another aspect of the present invention, a vehicle accessory for mounting in a vehicle is provided that comprises a sensor device comprising a support structure; a sensing element mounted on the support structure for sensing optical radiation and generating an electrical output in response thereto; and an encapsulant encapsulating the sensing element on the support structure, the encapsulant including an integral anamorphic lens.
According to another aspect of the invention, a sensor device comprises a support structure; a sensing element mounted on the support structure for sensing optical radiation and generating an electrical output in response thereto; and an encapsulant encapsulating the sensing element on the support structure, the encapsulant including an integral lens for directing incident optical radiation toward the sensing element, the lens having different focal lengths for transverse directions.
According to another aspect of the present invention, a sensor device comprises a support structure; a sensing element mounted on the support structure for sensing optical radiation and generating an electrical output in response thereto; and an integral encapsulant configured to encapsulate the sensing element on the support structure, the encapsulant having at least a first zone and a second zone, the second zone exhibiting at least one different characteristic from the first zone.
These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.